Análise químico ambiental da bacia do Rio Santo Antônio - MG por meio da avaliação de amostras de água e sedimentos.

Abstract

The Santo Antônio river basin, located in the eastern portion of the state of Minas Gerais, is the largest and most preserved among the tributaries of the Doce river basin. However, this has been increasingly impacted by human action, due to population growth and increasing mining activities. This mastersought to understand the influence of geogenic and anthropogenic actions on the chemical composition of water in the Santo Antônio river basin. For this, the sampling campaign was carried out in September 2019 (dry period) and water and sediment samples were collected at 16 previously selected points to raise parameters for this environmental analysis. In the field, physical and chemical analyses of water were carried out, and in the laboratory, chemical information of water and sediments were carried out by ICP-OES, and the results were submitted to statistical treatments. Furthermore, the study of sediments still involved granulometric and mineralogical analyses. Regarding the physical and chemical parameters of water, it was observed that the parameter "dissolved oxygen in water" is outside the standards determined for class 2 of the CONAMA 357/2005 standard at the headwaters of the Santo Antônio river, in Conceição do Mato Dentro. Regarding the chemical parameters obtained in laboratory from the water, it was found that there is a high concentration of Fe in specific points of the upper and middle Santo Antônio, close to mining areas, as well as a high concentration of Fe and Mn elements at the confluence between Santo Antônio and Doce river, due to the influence of the main river on its tributary. The granulometric analyzes suggest that the coarsest sediments, predominant in the basin, are an obstacle to the adsorption of potentially toxic metals and these act as an important factor in the degradation of organic matter. The mineralogical analysis revealed that the geological substrate of the basin reflects the mineralogy of the regional geological framework. The chemical composition of the sediments indicates that there is contamination of As (confluence of the Santo Antônio river), Cd (Jirau stream, middle Santo Antônio river and Guanhães river), and Cr (Guanhães river and Santo Antônio river confluence) in the basin, a from the comparison with data from CONAMA regulation 454/2012. The statistical treatment allowed to correlate the chemical data of water and sediments with the local lithology. Thus, there was a positive correlation between the following groups of elements: Ca- Mg-K-Na, Fe-Mn-Co, Cr-Ni, Cu-Zn and Pb-Ti. The geoaccumulation index showed that several points in the basin drainages have good conditions to shelter life and supply the population with good quality water.